In a heavy stockpot over high heat, sauté the ground lamb and beef until browned (about 8 minutes). Remove the meat from the pan and set aside. Add sweet potatoes, parsnips, and pearl onions to the pot and sauté 5 minutes. Add the tomato paste, garlic, rosemary and cook 2 minutes. Stir in the flour and cook 1 minute.

Add the beer, broth, Worcestershire and mustard. Add the meat back into the pot and bring to a boil. Cook for 15-20 minutes. Add salt and pepper to taste. Serve.